2. XF86Config Options

The following options are of particular interest for the SiS
driver. Each of them must be specified in the Device section of the
XF86Config file for this card.

Option "SetMclk"

This option lets you to modify the memory clocking of your card.
(only for 5597 and 6326) Modifying the memory timings can destroy the
device, but usually the only ill effects of overclocking is to
have some noise an drawing errors, but BE CAREFUL. Usually a little
increment can improve the drawing speed, and allows also higher dotclocks.
The server reports default memclock on starting messages, so take it
as a base. Units are in KHZ.

Option "DacSpeed"

This option lets you to modify the maximum allowed dotclock).

Option "sw_cursor", "hw_cursor"

The default is for using the hardware cursor.

Option "Turboqueue"

5597/8 and 6326 have the option to extend the engine command queue on
VRAM. With extended queue length, the driver only checks queue status
on some color-expansion commands. This gives some performance improvement,
but is possible to lose some commands, corrupting screen output. As the
size of extended command queue is 16-32K, the probability is very low, but
exists. The performance gain observed is around 8-10%. Currently, using
this option will occasionally freeze the acceleration engine, causing
weird image display.

The SiS chips can only directly address 4096K
bytes of video RAM. Some video cards using these chips are
shipped with additional video RAM. The videoRAM must be
explicitly limited to 4096 for those cards. Attempting to use
the additional RAM leads to a variety of scrambled screen
artifacts.